This invention relates to the field of material processing using laser beams.
Material machining of electronic components (printed circuit boards-PCB, printed wire boards-PWB etc.) using laser beams is used to generate fine holes in flexible and hard materials. The density requirements of electronic components is increasing at a rapid rate and utilization of real estate (on a PWB or PCB) is also increasing. Small through holes are very costly to produce, which has reduced acceptance in the industry. Blind holes or vias (i.e. holes that do not pass completely through a multi-layered printed wiring board) make more efficient use of PWB real estate, but are expensive to produce.
U.S. Pat. No. 5,676,866 issued on Oct. 14, 1997 discloses a laser beam drilling process. The laser beam is spatially divided into many beams each of which hits a mirror element and is directed down onto the workpiece through a single focusing lens. A particular mirror element cannot direct a laser beam to all portions of the lens field area because the lens acts as a physical aperture to block some beam paths to the lens field.
The beams do not move during the actual drilling process (i.e. it is a percussion process not a trepanning process). U.S. Pat. No. 5,676,866 teaches the division of a large area beam into a large number of beamlets to do simultaneous processing of all the elements in one field, then move the sample to the next field.
This is a common scheme to utilize the beam from a laser with a high pulse energy efficiently in order to machine many holes in parallel where the energy to drill each hole is small.
An object of the present invention is to provide an apparatus for focusing multiple laser beams through a single scan lens.
Another object of the present invention is to provide a method of passing multiple differing beams through a single lens.
Another object of the present invention is to provide a method of passing multiple beams through a number of different lenses to provide parallel processing support.
Another object of the present invention is to provide a method of beam splitting and energy balancing to create multiple beams.
Another object of the present invention is to provide a method of beam shuttering using beam positioning galvanometers.
Another object of the present invention is to provide a multi-beam imaging system using path length balancing.
Another object of the present invention is to provide a method of alternating beams from different angles to improve feature quality.
Another object of the present invention is to provide a method of compensation for workpiece thickness variations to correct for beam position errors resulting from beam angle.
In accordance with one aspect of the present invention there is provided a material machining apparatus for machining a workpiece, said apparatus comprising: supply means for supplying a plurality of discrete machining beams that are separate from each other; deflecting devices, one for each of the plurality of discrete machining beams, for deflecting one of the plurality of discrete machining beams to generate multiple independent beams at a plurality of positions within a field of operation on the workpiece; a scan lens having an entrance pupil, said entrance pupil being configured to receive the multiple independent beams from the deflecting devices, said deflecting devices being located proximate to the entrance pupil of the scan lens; and control means for controlling said deflecting devices to change the respective positions of the multiple independent beams in at least one co-ordinate direction within the field of operation.
In accordance with another aspect of the present invention there is provided a material processing apparatus for machining a workpiece using a first laser source operating at a wavelength xcex1 generating a first source beam and a second laser source operating at a wavelength xcex2 generating a second source beam, said apparatus comprising: means for angularly dividing each of the first and second source beams to generate a plurality of beamlets associated with each of the first and second source beams whereby each beamlet approximately matches the respective source beam at a lower intensity; means for focusing the beamlets of each of the first and second source beams; and means for separately controlling each focused beamlet of each of the first and second source beams to scan the focused beamlets with a via being drilled in the workpiece, whereby when one of the beamlets is completed processing at a first position it can move to another position. In accordance with another aspect of the present invention there is provided a material machining apparatus for machining a workpiece, said apparatus comprising: supply means for supplying a plurality of discrete machining beams that are separate from each other; deflecting devices, one for each of the plurality of discrete machining beams, for deflecting one of the plurality of discrete machining beams to generate multiple independent beams at a plurality of positions within a field of operation on the workpiece; a plurality of scan lenses each having an entrance pupil, the plurality of discrete machining beams each being directed through the plurality of scan lenses each with said deflecting devices proximate to the entrance pupil of a respective one of the plurality of scan lenses; and control means for controlling said deflecting devices to change the respective positions of the multiple independent beams in at least one co-ordinate direction within the field of operation.
In accordance with another aspect of the present invention there is provided a method of machining a workpiece using a laser comprising the steps of (a) supplying a plurality of discrete machining beams that are separate from each other generated from the laser; (b) deflecting each one of the plurality of discrete machining beams to generate multiple independent beams at a plurality of positions within a field of operation on the workpiece; (c) receiving and outputting the multiple independent beams received at an entrance pupil of a scan lens; and (d) changing the respective positions of the multiple independent beams in at least one co-ordinate direction within the field of operation.
In accordance with another aspect of the present invention there is provided a method of drilling a via in a workpiece using a first laser beam and a second laser beam where the first laser beam and the second laser beam converge at the workpiece at an incident angle, said method comprising alternatingly pulsing the first laser beam and the second laser beam until the via is formed on the workpiece.